The increasing demand for the transportation of large volumes and great weight over long distances demands aircraft with great lift capabilities, capabilities far in excess of those afforded by present designs. Conventional heavier-than-air planes designed for large, heavy cargoes, require considerable power and speed in order to remain airborne. While present aircraft structures can transport weights and volumes which are amazing, they challenge the limits of present technology. Indeed, major advances in aircraft design and engine technology would be required to extend the payload capability of such structures substantially. In addition, the limitations posed simply by the length of available runways prohibit in a practical sense appreciable extension of conventional present heavier-than-air plane structures.
Lighter-than-air(LTA) crafts have been proposed to lift and transport large, heavy volumes. However, historically such LTA craft have been capable of carrying only relatively light payloads compared to their physical size. As the size of an LTA craft is increased, it is possible, due to the "cube law" (which shows that minor increases in dimension vastly increase volume, i.e., 1 foot cubed = 1 cu. ft. whereas 2 feet cubed - 8 cu. ft.), to reduce the relative weight of the framework envelope and other structure. Thus, although in small sizes the rigid airship cannot compete with the non-rigid or the airplane because its structural weight is prohibitive, as the size increases the weight of the rigid framework becomes less critical. The last commercially operated airship, the leviathan Hindenburg also known as LZ 129, which was destroyed in a disasterous fire at Lakehurst, New Jersey on May 6, 1937, was the largest dirigible (i.e., "steerable") airship ever launched. It was 804 feet long and 147 feet high. Built in Germany under the direction of the famous Dr. Hugo Eckner, "Hindenburg" contained over 7 million cubic feet of hydrogen gas with a useful lift (buoyancy) of 230 tons (460,000 lbs.). This great ship carried 40 crew members, 72 passengers and up to 25,000 pounds (12.5 tons) of cargo. To provide a larger lifting capability, such a structure in turn must be so large that the aerodynamic load imparted by atmospheric forces would determine its direction unless extremely powerful (therefore heavy) propulsion means were provided. Lighter-than-air crafts to date have used a constant differential pressure envelope to contain the buoyant gas. This envelope modulated its volume, typically helium, dependent upon altitude and temperature, breathing in (or out) ambient air to maintain overall vehicle volume constant. Such an arrangement in turn requires balloonettes to segregate the helium buoyancy volume from the air ballast volume to prevent mixing and loss of helium. For these reasons, conventional structures do not offer such promise for meeting the developing demand for transporting large volumes of heavy goods.
To solve such problems and meet this demand, this disclosure describes an aircraft that provides a means to achieve a constant envelope allowing the pressure to vary with altitude and temperature while at the same time provides other means to achieve inherent stability and enhance manueverability both in flight and on the ground.